Need help with Prime number Loop and with boolean statement

[Kwasi Roberts]

Can someone tell me where I'm going wrong here in making this read all prime numbers
import java.util.*;

Here is my original code

public class PrimeV1{

  public static void main(String[] args)
  {
    Scanner input = new Scanner(System.in);
    int count;
    int i;
    int x;
    int sum;
    System.out.println("Enter a positive integer");
    x = input.nextInt();
    i = 1;
    sum = 0;
    count = 0;
    while (x % i != 0 && i <=x)
    {
    sum = sum + x;
    i = i + 1;
    count++;
    {

    }
    System.out.println( + x + " Is a Prime Number ");
   }
  }
}

Here is the code where I was asked to combine a while loop with a boolean statement. I need help on both.

public class isPrime4 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {

		// change this to test all numbers 1 - 1000

		for (int i=1; i <= 1000; i++)
		{

			System.out.println(+ i + " is a Prime Number " );

	}


	static public boolean isPrime(int number) {

		int  half = number / 2;

		for ( int counter = 2; counter <= half ; counter++){
			if ( number % counter == 0   )
				return false;

		}
		return true;
	}
}

[Edit: put code between [code] and [/code] ubb code blocks]

[Andrew Monkhouse]

For the first class:

What is the definition of a Prime number? How are you handling the two conditions to validate that it is a prime?

What are you trying to do in lines 20 - 22?

[Campbell Ritchie]

You are both mistaken using ½ the number as the limit for testing whether it is prime. You ought to use √number. You also should use a Sieve of Eratosthenes to populate a boolean array and that will tell you whether a number is prime or not. Much faster and efficient than using the % operator. If you look in the Wikipedia article which appears from that link, there is the Sieve of Euler, too.

[Andrew Monkhouse]

vinayak jog - thank you for replying, however at CodeRanch we work on the theory that we want to teach people how to solve the problems themselves. Complete solutions don't lend themselves to that - the learning experience is removed.

I therefore removed your response.